I recently got a Linksys WRT 1900ACS and first thing i did was install OpenWRT i love the software and the community.
I've got an odd problem where iPerf3 from 1 site to another site works fine, but i have slow throughput one way but only from a client machine connected to the 1900ACS. If i Run iPerf3 on the router i get good throughput.
for example
Site 1 server 1 -> Sophos XG (192.168.1.1) -------ipsec----->Linksys WRT1900ACS (192.168.2.1) =36Mbps
Site 1 server 1 -> Sophos XG (192.168.1.1) -------ipsec----->Linksys WRT1900ACS (192.168.2.1) -> Site 2 Server 2 = 36Mbps
Linksys WRT1900ACS (192.168.2.1) -------ipsec-----> Sophos XG (192.168.1.1) -> Site 1 server 1 = 50Mbps
The problem occurs when running iPerf from a server or client behind the Linksys router and its sending data ;
Site 2 Server 2 ->Linksys WRT1900ACS (192.168.2.1) -------ipsec-----> Sophos XG (192.168.1.1) -> Site 1 server 1 = 3Mbps
Site 1 is Virgin Media running at 1500MTU
Site 2 is BT FTTP PPPoE running at 1500MTU (Baby Jumbos)
As the through put is fine from the OpenWRT Router i'm assuming the ipsec tunnel is correctly configured and MTUs are all good.
I Should also mention that Site 1 has a IPSec connection to Azure and Iperf to a virtual machine hosted there works fine.
Routing and NAT appears to be okay as everything is working just a bit slow as described.
I'd appreciate any help or pointers anyone can give.